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Impedance analysis of the isolated epithelium of frog skin (northern Rana pipiens) was carried out in the frequency range between 0.1 Hz and 5.5 kHz while Na+ transport was abolished. Under these conditions, the impedance is determined almost completely by the dielectric properties of the apical membranes of the cells and the parallel shunt resistance. The(More)
Aldosterone, a steroid hormone, regulates renal Na+ reabsorption and, therefore, plays an important role in the maintenance of salt and water balance. In a model renal epithelial cell line (A6) we have found that phosphoinositide 3-kinase (PI 3-kinase) activity is required for aldosterone-stimulated Na+ reabsorption. Inhibition of PI 3-kinase by the(More)
To study and define the early time-dependent response (< or = 6 h) of blocker-sensitive epithelial Na+ channels (ENaCs) to stimulation of Na+ transport by aldosterone, we used a new modified method of blocker-induced noise analysis to determine the changes of single-channel current (iNa) channel open probability (Po), and channel density (NT) under(More)
Blocker-induced noise analysis and laser scanning confocal microscopy were used to test the idea that cAMP-mediated vesicle exocytosis/endocytosis may be a mechanism for regulation of functional epithelial Na+ channels (ENaCs) at apical membranes of A6 epithelia. After forskolin stimulation of Na+ transport and labeling apical membranes with the fluorescent(More)
Measurements of transepithelial electrical impedance of continuously short-circuited A6 epithelia were made at audio frequencies (0.244 Hz to 10.45 kHz) to investigate the time course and extent to which prostaglandin E(2) (PGE(2)) modulates Cl(-) transport and apical membrane capacitance in this cell-cultured model epithelium. Apical and basolateral(More)
Although a variety of hormones and other agents modulate renal Na+ transport acting by way of the epithelial Na+ channel (ENaC), the mode(s), pathways, and their interrelationships in regulation of the channel remain largely unknown. It is likely that several hormones may be present concurrently in vivo, and it is, therefore, important to understand(More)
The serum and glucocorticoid induced kinase 1 (SGK1) participates in the regulation of sodium reabsorption in the distal segment of the renal tubule, where it may modify the function of the epithelial sodium channel (ENaC). The molecular mechanism underlying SGK1 regulation of ENaC in renal epithelial cells remains controversial. We have addressed this(More)
Methods of blocker-induced noise analysis were used to investigate the way in which forskolin and vasopressin stimulate Na transport at apical membranes of short-circuited frog skin transporting Na at spontaneous rates of transport. Experiments were done under conditions where the apical Ringer solution contained either 100 mM Na or a reduced Na(More)
Blocker-induced noise analysis of epithelial Na(+) channels (ENaCs) was used to investigate how inhibition of an LY-294002-sensitive phosphatidylinositol 3-kinase (PI 3-kinase) alters Na(+) transport in unstimulated and aldosterone-prestimulated A6 epithelia. From baseline Na(+) transport rates (I(Na)) of 4.0 +/- 0.1 (unstimulated) and 9.1 +/- 0.9(More)